Electric discharge device



June 21, 1938. E..F. LOWRY ET AL ELECTRIC DISCHARGE DEVICE Filed Aug. 29, 1936 Ibo Time

INVENTQRS- and d the cathode begins to cool.

Patented June 21, 1938 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE DEVICE Application August 2-9, 1936, Serial No. 98,470

- 17 Claims.

Our invention relates to electric discharge apparatus and it has particular relation to apparatus for delaying the initiation and interruption of current supply to a load.

It is an object of our invention to provide an accurate time delay relay which shall be simple and inexpensive.

Another object of our invention is to provide a time delay relay that shall open and close with a predetermined time delay which may be varied at will.

More specifically stated, it is an object of our invention to provide a system for introducing a time delay in the application of power to a load and the interruption of the supply of power to the load, the time delay in the former instance being, at the will of the operator, the same as or diiferent than the time delay in the second instance.

In the practice of our invention, we utilize the time delay involved in the operation of the discharge device shown and described in a copen-d ing application, Serial No. 43,347, filed October 3, 1935, Patent No. 2,100,195, dated November 23, 1937, to Erwin F. Lowry, and assigned to the Westinghouse Electric & Manufacturing Company. The discharge device in question comprises an anode and a cathode and a shield enclosing the cathode. The shield operates to delay the transmission of current between the anode and the cathode until the cathode is heated to a predetermined temperature. Accordingly, if anode potential and cathode energizing potential are simultaneously applied to the discharge device, the discharge device is energized a predetermined interval of time after the application of potential. At this point, the load to be energized is supplied with current.

When the supply of current is to be interrupted, the anode circuit and the heating circuit for the cathode of the discharge device are simultaneously interrupted. The supply of current through the discharge device is interrupted and In accordance with our invention, we provide a second discharge device connected in parallel with the first discharge device, which, when the anode circuit of the first discharge device is opened, becomes energized and continues the supply of current to the load.

' The control circuit of the second discharge device To avoid superfluous verbiage in the claims, we

shall here define the discharge device which is disclosed in the above-mentioned Lowry application as a shield-cathode discharge device or a discharge device of the shield-cathode type. Accordingly, a shield-cathode discharge device for the purpose of this application is a discharge device having at least one emissive cathode, an electrode cooperating therewith as a charge-collecting electrode, and a shield enclosing the cathode, which, when heated, emits electrons to the oathode. In practice, a suitable circuit is connected between the shield and the cathode of a shieldcathode discharge device which provides for the application of a blocking potential to the shield as long as the cathode and the shield are cold. However, when the shield becomes heated by reason of heat radiation from the cathode, the eifect of the blocking potential is neutralized and a discharge passes between the collecting electrode and the cathode of the discharge device. It is apparent, of course, that the discharge device of the shield-cathode type may be asymmetric in 9 structure, and accordingly may have a non-emissive electrode and an emissive cathode. It may also, however, be symmetric in structure and have two emissive electrodes, each of which is provided with a shield. The term shield cathode dis- 3 charge device, or its equivalent, is used herein with the understanding that it encompasses any device in which the specific features of the Lowry discharge device are involved.

The novel features that we consider characteristic of our invention are set forth with particularity in the appended claims. The inven-' tion itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, in which:

Figure l is a diagrammatic view showing a preferred embodiment of our invention; and

Fig. 2 is a graph illustrating the operation of our invention.

The apparatus shown in Fig. 1 comprises a discharge device I of the shield-cathode type having an anode 3, an emissive cathode 5, and. a shield l enclosing the cathode, as is explained in the above-mentioned co-pending Lowry application. The electrodes 3, 5 and I are enclosed in a gas-tight envelope 9 in the usual manner. In the envelope 9 an ionizable medium, such as a noble gas or the vapor of a globule of a metal such as mercury, is present.

Anode potential is supplied to the discharge device I by a secondary section II of a supply transformer I3, and cathode heating current is supplied by another secondary section I5 of the transformer. A double-pole switch I1 is provided for simultaneously closing the anode and cathode circuits. When this switch is operated to close the circuits, the temperature of the cathode COll'lmences to rise. However, a discharge does not take place in the discharge device I by reason of the fact that the shield 1 is connected through a variable resistor IE! to the negative terminal of a battery 2|, the positive terminal of which is connected to the cathode 5.

As is explained in the Lowry application, the shield 1 is capable of electron emission, and as it is heated by the radiation from the cathode 5, electrons pass from the shield to the cathode under the action of the battery 2|. A potential drop tending to neutralize the effect of the source 2| is, therefore, produced across the resistor I9, and this drop continues to increase as the temperature of the shield 1 increases until the effect of the battery is totally overcome and the discharge device passes current. The exciting coil 23. of a relay 25 in circuit with the discharge device I is energized when the discharge device I passes current. When the relay 25 is thus encrgized, its .upper movable contactor 21 closes a work circuit 29 to perform whatever function is to be performed.

The time delay involved in the operation of the relay is determined by the magnitude of resistor I9 in circuit with the shield I. This is illustrated in the graph shown in Fig. 2. In this graph, the difference of potential between the shield and the cathode is. plotted as ordinate and the time in seconds which elapses between the closing of the double-pole switch I1 and the excitation of the discharge device I is plotted as abscissa for different resistors in the shield circuit. The family of full line curves 3|, each of which corresponds to a resistance I9 of different magnitude, illustrates how the negative difference of potential varies as a function of time. In each case, the absolute value of the potential between the shield 1 and the cathode 5 decreases as the time of heating the shield increases until a point 33 is attained, at which the discharge device commences to pass current. We have found that the greater the magnitude of the resistor IS, the longer is the interval of time between the closing of the switch I1 and the excitation of the discharge device I. By adjusting the resistor I9 to a proper magnitude, the delay in the operation of the relay 25 following the operation of the double-pole switch I1 may be predetermined at will. While we have illustrated the resistor I9 as having a movable top, this showing should be regarded merely as symbolical, since, under certain circumstances, it may be desirable to utilize a plurality of independent resistors and a movable contactor for selecting one of them, as is illustrated, for example, in Fig. 5 of the copending Lowry application.

When the double-pole switch I1 is opened, the anode circuit and the cathode heating circuit are simultaneously disconnected from their respec-= tive secondary supply sections II and I5. The cathode 5 and the shield 1 now begin to cool and the negative potential difference between the shield and the cathode now rises. The rise of the potential difference for any given resistor iii in the shield circuit corresponds to the decrease in the potential diiference for the same resistor. A single broken line curve 35 is plotted to illustrate the cooling situation in one case. It is understood, of course, that there is a family of curves 35 just as there is a family of curves 33. From the above observations, it will be seen that by selecting a proper magnitude for a resistor such as IE3 in series with the shield 1, the cooling of the shield and, therefore, the time required for the potential between the shield and the cathode to become equal to the potential of the battery 2% may be predetermined. If the latter time interval is to be different than the time interval involved in the excitation of discharge device I, a different shield circuit, including a resistor 31 different magnitude than the resistor is, may be provided. The shield circuit, including the resistor 31, is closed by a movable contactor 39 of the relay 25 when the relay is energized, and at the same time a movable contactor 4i which had maintained the shield circuit including resistor I9 closed, opens the latter circuit. In the embodiment illustrated, the resistance 31 is smaller than the resistance I9, and accordingly the time delay involved in the opening or" the work circuit 29 is smaller than the time delay involved in its closing.

It will be noted that in the description of the system thus far we have only shown that a time delay involved in the deenergization of discharge device I. However, the time delay involved in the cooling of shield 1 cannot be directly used to control relay 25, since both the anode circuit and the cathode heating circuit of the discharge device i are opened simultaneously. The cathode heating circuit, must of course, be opened to enable the cathode to cool and time the opening operation of the tystem. The anode circuit must be opened, because unless it is opened, a discharge will persist in the discharge device I and the cathode 5 will be maintained heated by the discharge current in spite of the fact that its own heating circuit is open.

Accordingly, to maintain the relay 25 energized while the shield 1 is cooling, we provide a second discharge device 43 having an anode 45, a cathode 41, and a control electrode 49. second discharge device 43 is not energized beiore the first discharge device I is energized, and

for this reason, its cathode heating circuit may be maintained open until the first discharge device I is energized. To accomplish this purpose, the heating circuit for the cathode 41 is normally open and the relay 25 is provided with a fourth movable contactor 5|, which, when the relay 25 is energized following the energization of discharge device I, closes the heating circuit.

The cathode 41 is supplied with heating current from a secondary section 53 of the transformer I3. The anode 45 is connected to the upper terminal of the secondary section II, whereby the anode potential is supplied to the discharge device I, through the exciting coil 23 of the relay 25 and it is accordingly connected to the anode 3 of the discharge device I when the double-pole switch I1 is closed. The cathode 41 of the discharge device 43 is connected to the cathode 5 of the discharge device I. Hence, when the discharge device I is energized and the excitation of the cathode 41 of the discharge device 43 is completed, the discharge device 43 does not become energized since the potential drop between its anode 45 and its cathode 41 is the same as the potential drop between the anode 3 The and cathode of the discharge device I, and this is too small to produce a discharge in the discharge device 43 as long as the former device remains energized. If necessary, a biasing source 55 may be connected to the control electrode 49 of the discharge device 43, and to make certain that the latter remains deenergized, discharge device I is energized.

When the discharge device I is deenergized by the opening of the double-pole switch II, the potential drop across the anode-cathode circuit of this discharge device becomes equal to the potential drop across the secondary section II of the transformer I3. The biasing potential 55 supplied to the control electrode 49 is then no longer sufiicient to maintain the discharge device 43 deenergized and it is immediately energized. The relay 25 may be provided with a lag loop 51 to prevent its becoming deenergized in the short interval of time between the deenergization of the discharge device I and the energization of the second discharge device 43. The relay 25 is, therefore, maintained energized after the discharge device I is deenergized by the current flowing through the second discharge device 43.

The control electrode 49 of the discharge de-- vice 43 is connected through the biasing potential 55 to the shield 'I of the discharge device I, and, therefore, the control circuit of the discharge device 43 includes the movable contactor 39 of there1ay25, the resistor 31, and the battery 2| associated with the shield I of the first discharge device I. As the cathode 5 and the shield I of the discharge device I now cool, the potential drop across the resistor 31 in circuit with the control electrode 49 of second discharge device 43 decreases, and, therefore, the negative potential difference between the control electrode 49 and the cathode 4'? increases. This varying condition persists until the potential between the control electrode 49 and the cathode 41 becomes sufficiently negative to deenergize the second discharge device causing the relay 25 to be deenergized and the work circuit 29 to open.

Our invention has been shown and described hereinabove as embodied in a specific system. Many of the features of this system are to be taken as symbolical. For example, in practice, it may often happen that other elements than a double-pole switch are utilized to simultaneously close the anode and the cathode circuits of the shield-cathode discharge device I. In particular, a photo-cell circuit or an inductance or capacity responsive circuit may replace the switch II. Hence, the double-pole switch I! is to be taken as symbolical of a general control element.

In the embodiment described hereinabove, and, in general, preferably, discharge devices I and 43 of the gas or vapor-filled type are utilized. It will be apparent, however, that our invention may be practiced with discharge devices of the high vacuum type, and, therefore, systems in which higl'i vacuum discharge devices are utilized in lieu of the gas-filled devices described in the preferred embodiment lie within the scope of our invention.

Although we have shown and described certain specific embodiments of our invention, we are fully aware that many modifications thereof are possible. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim as our invention:

1. In combination, a first current path, a second current path, means tending to cause a current to flow in said current paths, the last said means being more effective in causing a current to flow in said first path than in said second path, whereby a current flows in said first path before it flows in said second path, means coop- .erative with said first path for preventing current from flowing in said second path when current flows'in said first path, and means for causing current to flow in said second path as a result of the interruption of current flow in said first path.

2. In combination, a first current path, means for causing a current to flow in said first current path an interval of time predeterminable at will after the occurrence of an operation, a second current path, means tending to cause a current to flow in said second path, means for rendering the last-said means ineffective before a current flows in said first current path, means cooperative with said first current path for rendering said current-flow-causing means ineffective while a current flows in said first path, and means for rendering said current-flow-causing means effective, on the interruption of a current in said first path, to cause a current to flow in said second path.

3. In combination, a first current path, means for causing a current to flow in said first current path an interval of time predeterminable at will after the occurrence of an operation, a second current path, means tending to cause a current to flow in said second path, means for rendering the last-said means ineffective before a current flows in said first current path, means cooperative with said first current path for rendering said current-flow-causing means ineffective while a current flows in said first path, means for rendering said current-fiow-causing means effective, on the interruption of a current in said first path, to cause a current to fiow in said second path, and means for interrupting the current fiow in said second path after an interval of time predeterminable at will.

4. In combination, a first current path, means for restraining current from flowing in said first path, a second current path, means for restraining a current from flowing in said second path for an interval of time predeterminable at will after an operation and thereafter causing a current to flow in said second path, the last means functioning to render said first-mentioned restraining means ineffective when a current is permitted to flow in said second path, means cooperative with said second path for restraining a current from flowing in said first path while a current fiows in said second path and means for interrupting current flow in said second path whereby current flows in said first path.

5. In combination, a first current path, a second current path, means for restraining current from flowing in said paths for an interval of time predeterminable at will after an operation and thereafter permitting current to fiow in said paths, current being permitted to flow in said first path before it is permitted to flow in said second path, and means cooperative with said first path for restraining current from flowing in said second path while current flows in said first path, whereby when the current is interrupted in said first path current is permitted to flow in said second path.

6. In combination, a first current path, a second current path, means for controlling the flow of current in said paths, said controlling means when actuated in one sense operating to restrain current from flowing in said paths for an interval of time predeterminable at will after the last said actuation and thereafter permitting current to flow and when actuated in the opposite sense after having been actuated in. the first sense operating to permit current to flow in said paths for an interval of time predeterminable at will after the last said. actuation and thereafter restraining current from flowing, means associated with said second path for restraining current from flowing in said second path, on the actuation of said controlling means in the first sense, until after current flows in said first path, and means cooperative with said first path for restraining current from flowing in said second path while current is flowing in said first path.

'7. In combination, a first current path, a sec- 0nd current path, means for controlling the flow of current in said paths, said controlling means when actuated in one sense operating to restrain current from flowing in said paths for an interval of time predeterminable at will after the last said actuation and thereafter permitting current to flow and when actuated in the opposite sense after having beenactuated in the first sense operating to permit current to flow in said paths for an interval of time predeterminable at will after the last said actuation and thereafter restraining current from flowing, means associated with said second path for restraining current from flowing in said second path, on the actuation of said controlling means in the first sense, until after current flows in said first path, means cooperative with said first path for restraining current from flowing in said second path while current is flowing in said first path, and means for interrupting current flow in said first path while said controlling means is actuated in said oppo site sense whereby current flows in said second path for an interval of time predeterminable at will and is thereafter interrupted.

8. In combination, a first current path, a sec- 0nd current path, means for controlling the flow of current in said paths to restrain and permit current to flow therein, means associated with said second path to restrain current from flowing in said second path when said controlling means has been actuated to permit current to flow in said paths, until after current has been permitted to flow in said first path, means cooperative with said first path to restrain current from flowing in said second path while current flows in said first path, and means for actuating said controlling means in one sense to restrain current from flowing in said first path for only an interval of time predeterminable at will after the said actuation and thereafter to permit current to flow in said paths, whereby current flows in said first path, and for actuating said controlling means in the opposite sense to interrupt current flow in said first path and to permit current to flow in said paths for an interval of time predeterminable at will alter the last said actuation and thereafter to restrain current flow in, said paths, whereby current fiows in said second path for said last-- mentioned interval of time.

9. In combination, a first discharge path hav ing a control electrode, controlling means when operated in one sense, cooperative with said control electrode for restraining a. discharge in said first path for an interval of time predeterminable at will after said operation and thereafter permitting a discharge and when operated in the opposite sense for permitting a discharge for an interval of time predeterminable at will af ter the last said operation and thereafter restraining it,

a second discharge path, and means cooperative with said first discharge path for restraining a discharge in said second path until after a discharge is interrupted in said first path.

10. In combination, a first dischage path having a control electrode, controlling means when operated in one sense cooperative with said control electrode for restraining a discharge in said first path for an interval of time predeterminable at will after the said operation and thereafter permitting a discharge, and when operated in the opposite sense for permitting a discharge for a predetermined interval of time and thereafter restraining it, a second discharge path, means cooperative with said first discharge path for restraining a discharge in said second path until after a discharge is interrupted in said first path, and means including said controlling means for interrupting the discharge in said second path after said last-mentioned predeterminable inter- L! val of time on the operation of said controlling means in said opposite sense.

11. In combination, an electric discharge device of the shield cathode type, means for impressing a principal potential on said discharge device, means for impressing a potential between the shield and the cathode of said discharge device, means ior energizing the cathode of said ischarge device, another discharge device having a plurality of principal electrodes and a control electrode, means for connecting the principal electrodes of said last-mentioned discharge device in parallel with the principal electrodes of said first-mentioned discharge device, and means for initiating a discharge in said last-mentioned discharge device as a result of the interruption only of a discharge in said first-mcntioned discharge device.

12. In combination, an electric discharge device of the shield cathode type, means for impressing a principal potential on said discharge device, means for impressing a potential between the shield and the cathodes of said discharge device, means for energizing the cathode of said discharge device, another discharge device having a plurality of principal electrodes, and a control electrode, means for connecting the principal electrodes of said lastmentioned discharge device in parallel with the principal electrodes of said first-mentioned discharge device, means for initiating a discharge in said last-mentioned discharge device as a result of the interruption only of a discharge in said first-mentioned discharge device, and means for connecting said control electrode to said shield, whereby the discharge in said last-mentioned device persists after the interruption of a discharge in said first-mentioned device for an interval of time corresponding to the circuit of said shield.

13. In combination, an electric discharge device of the shield cathode type, means in circuit with the shield and the cathode of said discharge device for supplying a potential between the shield and the cathode, a source for supplying principal potential to said discharge device, a source for supplying energy to said cathode, means for simultaneously connecting and disconnecting said potential-supply source and said energy supply source to said discharge device, another discharge device having principal electrodes and a control electrode, means for connecting the principal electrodes of said lastnamed discharge device in parallel with the principal electrodes of said first-named discharge device, means functioning to energize said lastnamed discharge device as a result only of the interruption of a discharge in said first-named device, a circuit for the control electrode of said last-named discharge device, and means for so connecting said circuit to the shield circuit of said first-named discharge device that current initiated in said last-named device persists only for an interval of time predetermined by the shield circuit of said first-named device.

14. Apparatus according to claim 13 characterized by means to be actuated when the firstnarned discharge device is energized for changing the constants of the shield circuit of said discharge device.

15. In combination, a first dischargedevice, said discharge device having an anode, a cathode and a control electrode, a source for supplying potential between the anode and the cathode of said first discharge device connected to said discharge device, a source for supplying energy to the cathode of said discharge device, a circuit for the control electrode of said discharge device, a second discharge device, said second discharge device being of the shield cathode type, a source for energizing the cathode of said second discharge device, means for simultaneously connecting and disconnecting said energizing source and said cathode and the principal electrodes of said second device in parallel with the principal electrodes of said first device, a circuit for the shield of said second deviceproviding for excitation of said second device a predetermined interval of time after said connecting and disconnecting means is operated to connect said first device, means to be actuated in response to the excitation of said second device for connecting the energizing source to the cathode of the first device, and means for so connecting the control circuit of the first device and the shield circuit of the second device that the first device is energized as a result of the interruption of a discharge in the second device and remains energized for an interval of time predetermined by the shield circuit of the second device.

16. In combination, an electric discharge device having a control electrode and a plurality of principal electrodes, an electric discharge device of the shield cathode type, a shield circuit for the last-named discharge device and means cooperative with said shield circuit for impressing a potential between the control electrode and a principal electrode of said first-named discharge device.

1'7. In combination, an electric discharge device having a plurality of principal electrodes, a shield-cathode discharge device and means cooperative with the shield of said last-named discharge device for controlling the discharge between the principal electrodes of said firstnamed discharge device.

ERWIN F. LOWRY. HYMEN DIAMOND. 

